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    <title>Document</title>
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<script>
    /*
    1.cnpm i -D @babel/core @babel/cli @babel/preset-env @babel/node
    2.cnpm i -S @babel/polyfill
    3.项目根目录创建文件 babel.config.js
        const presets = [
            ["@babel/env",{
                targets:{
                    edge:"17",
                    firefox:"60",
                    chrome:"67",
                    safari:"11.1"
                }
            }]
        ];
        module.exports = {presets};
    4.通过npx babel-node router.js  执行代码
    * */
</script>
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